The present invention relates in general to protective coatings, and in particular to a heat absorbing coating comprising micro-encapsulated heat absorbing material such as phase change material dispersed throughout a carrier, and additionally includes a substrate having such a coating and methodology for thermally protecting a substrate.
Certain substrates that are subjected to environments that produce heat in the substrates can have significantly is reduced lifetimes because they do not possess sufficient durability to withstand thermal erosion. One example of a group of such substrates is found in aircraft structures. Specifically, most modern jet aircraft structures require the use of advanced materials that achieve product cost effectiveness. However, because of the high-speed environment in which these structures operate and the attendant heat generated therefrom, thermal erosion durability of the structures, and especially highly vulnerable portions thereof such as leading edges and engine exhaust nozzles, is reduced to considerably less than desirable for efficient and economical operations.
The use of micro-encapsulated thermal absorbing material has been taught, for example, for temperature control by incorporation in potting materials, slurries, building structures such as concrete and gypsum board, solar collecting structures, and alloys used in solar-steam systems. Disclosed thermal absorbing material includes phase change materials, while disclosed encapsulant materials include metals and polymers. However, none of these prior-art application provides or suggests any structural treatment beyond incorporation of encapsulated thermal-absorbing material within the structure. Consequently, thermal erosion of the surface of a substrate is not addressed.
In view of the potential for thermal degradation of structural surfaces exposed to significant heat, it is apparent that a need is present for a surface coating that can function to thermally manage environmentally produced heat erosion at the sites of damage. It is therefore a primary object of the present invention to provide a heat absorbing surface coating including a micro-encapsulated heat absorbing material dispersed in a carrier medium for application to a substrate.
Another object of the present invention is to provide a heat absorbing surface coating wherein the carrier medium is a sprayable polymer matrix.
Yet another object of the present invention is to provide a substrate having a heat absorbing surface coating thereon comprising a micro-encapsulated phase change material dispersed in a carrier medium for application to a substrate.
Still another object of the present invention is to provide methodology for thermally protecting a substrate comprising the application on the substrate of a heat absorbing surface coating including a micro-encapsulated heat absorbing material dispersed in a carrier medium.
These and other objects of the present invention will become apparent throughout the description which now follows.
The present invention is a heat absorbing coating comprising a plurality of micro-capsules each comprising an encapsulant shell and a heat absorbing material within the shell, and a carrier adherable to a substrate and throughout which the micro-capsules are dispersed The heat absorbing material is preferably a phase change material and can be non-limitedly chosen from the group consisting of polyethylene, polypropylene, polywax, and combinations thereof which may have a melting point between about 425xc2x0 F. and about 475xc2x0 F. Shell material can be a metal such as copper, for example, or a polymer. The carrier can be a sprayable polymer mix which provides significant efficacy in uniform application to a substrate.
The present invention includes a substrate having thereon the above inventive coating, with the substrate exemplified by an aircraft structure, such as, for example, a leading edge or an engine exhaust nozzle, that experiences extreme heat in its operating environment. A structure so coated is significantly protected from thermal erosion, with methodology accomplishing such protection comprising the application of the above described coating onto a substrate in an amount sufficient to absorb a sufficient amount of heat and thereby prevent or significantly inhibit thermal degradation.